1. Field of the Invention
The present invention relates generally to a message processing method for a CDMA communication system, and in particular, to a method for processing user data and message to be transmitted over a common channel.
2. Description of the Related Art
Code division multiple access (CDMA) mobile communication systems, which have conventionally provided a voice-based service, can now provide a high speed packet data service. In a mobile communication system which mainly provides a voice service, control information is generally generated during call setup, handoff and call release. The control information is mostly Layer 3 (i.e., network layer) control messages and is transmitted over a signaling channel.
However, packet data has a bursting property which means that data is not continuously generated. Accordingly, taking into consideration the limited capacity of radio resources, the capability of mobile stations and the limited power consumption of mobile stations, a system providing a packet data service assigns a dedicated channel only when traffic is generated, instead of continuously assigning a dedicated traffic channel and a dedicated control channel to every user over the service time. Upon completion of transmitting the packet data, the system releases the dedicated channel in use after lapse of a predetermined time so as to enable other users to use the resource. To this end, a medium access control (MAC) sublayer is provided between a physical layer (i.e. Layer 1) and a link layer (i.e., Layer 2), to more effectively use the limited resources of the system. Control information generated in the MAC sublayer is transmitted over a MAC channel.
FIG. 1 illustrates state transition performed in a CDMA mobile communication system. The system is initially in a physical layer independent control function (PLICF) null state 111, when there is no service request. When a service request occurs in the null state 111, a base station and a mobile station exchange information required for the service through a common channel to connect a service option and establish a dedicated MAC channel (dmch) and a dedicated signaling channel (dsch), thereby to transition to a control hold state 113 where a message generated in the MAC sublayer and a control message generated in Layer 3 are exchanged between the mobile station and the base station.
When establishment of a dedicated traffic channel (dtch) for transmitting user data is completed in the control hold state 113, the base station and the mobile station transition to an active state 117 to exchange high speed packet data. A sequence number and an acknowledgement required indicator (ACK_REQ), generated in a radio link protocol (RLP) for securing reliable transmission, are added to the user data and then transmitted through a dedicated traffic channel. In the active state 117, every dedicated channel can be used; specifically, user data is transmitted over a dedicated traffic channel, and control information generated in the Layer 3 and control information generated in the MAC sublayer are transmitted over the dedicated signaling channel and the dedicated MAC channel, respectively, as in the control hold state 113.
When data is not generated for a predetermined time in the active state due to the property of the packet data, the base station and the mobile station release the dedicated traffic channel and then transition to the control hold state 113. In the control hold state 113, the dedicated signaling channel and the dedicated MAC channel are connected.
When data to be transmitted is not generated for a predetermined time in the control hold state 113, even the dedicated signaling channel and the dedicated MAC channel are released, and then a transition occurs to a suspended state 115 where only common channels are established. In the suspended state 115, information about the service and the dedicated channels are maintained so that upon generation of data to be transmitted over the dedicated channels, it is possible to reestablish the dedicated channels in a short time and then transition to the active station 117. When data to be transmitted is not generated for a predetermined time in the suspended state 115, the service information and the dedicated channel information, which have been holding the service, are deleted and then a transition to the null state 111 occurs.
In the suspended state 115 of FIG. 1, every dedicated channel is released and only the common channels exist. At this point, short data bursts (SDB) are transmitted by a radio burst protocol .(RBP) entity. To secure reliable transmission by the RBP entity, control files for a sequence number and an acknowledgement required indicator ACK_REQ are added by an automatic repeat request (ARQ) function block, a mobile station identifier (MSID) for identifying a data transmitter or receiver is added by an address function block, and then those are transferred to a common traffic channel mapping entity. Prior to being transferred to a common channel mapping entity, a length field and an error checking control field are added to the user data. The radio burst protocol generates one entity for every service and one mobile station can simultaneously provide one or more services, so that a service identifier is added to the user data in the common traffic channel mapping entity. The user data transferred to the common traffic channel mapping entity is mapped with a physical channel and transmitted to a receiver of the other party.
FIG. 2 is functional block diagrams illustrating a control plane 210 and a data plane 220 for a mobile communication system providing a data service. FIG. 3 is a detailed diagram of a function block in the data plane 220 of FIG. 2, for processing user data transmitted over a common traffic channel (ctch) and a MAC message transmitted over a common MAC channel.
Referring to FIG. 3, a radio burst protocol (RBP) entity 222 processes the short burst user data generated in the suspended state 115, a signaling radio burst protocol (SRBP) entity 224 processes a control message generated in Layer 3, and a control channel burst protocol (CCBP) entity 226 processes a control message generated in the MAC sublayer.
When short burst user data is generated in the suspended state 115, one to seven filler (i.e., xe2x80x9c0xe2x80x9d) bits are inserted in the short burst user data to construct the data in units of a byte (one byte=8 bits). Further, a length field LEN for indicating a length of the data and a cyclic redundancy check (CRC) code for error checking at a receiver are added and then transferred to a common traffic channel mapping entity. In the common traffic channel mapping entity, a service identifier (SID) for identifying data generated in the radio burst protocol of various services and a mobile station identifier MSID for identifying a data transmitter are added and then transferred to the common control channel/paging channel/access channel (CCCH/PCH/ACH) mapping entity.
When a Layer 3 control message is generated in the suspended state 115, a sequence number is assigned for securing reliable transmission in an upper link access control (LAC) sublayer, a mobile station identifier MSID is added, and then transferred to the signaling radio burst protocol entity 224. The signaling radio burst protocol entity 224 inserts xe2x80x9c0xe2x80x9d bits in the control message to generate the data on a byte unit basis, as in the radio burst protocol entity 222, adds a length field indicating a length of the data and an error checking code, and then transfers it to the common control channel/paging channel/access channel mapping entity.
A MAC message generated in the suspended state 115 is provided to the control channel burst protocol (CCBP) entity 226 after a service identifier is added thereto, in a common MAC channel mapping entity. The MAC message is then processed in the control channel burst protocol entity 226 and transferred to the common control channel/paging channel/access channel mapping entity to be mapped to the physical channel. Here, as shown in FIGS. 2 and 3, the common MAC channel message is not yet defined. That is, in the suspended state, when a control message generated in the Layer 3 is transmitted over the common channel, it plays a role of securing reliable transmission in the link layer which is the Layer 2. However, for the MAC message, a function for securing the reliable transmission is not defined.
As described above, in a mobile communication system which mainly provides a voice service, Layer 2 provides the above function for securing reliable transmission for the control information generated in the Layer 3. Therefore, in the case where control information generated in the MAC sublayer is transmitted over a common MAC channel, there is required a protocol for performing the above control function before the control information is transferred to the physical channel. In addition, it is necessary to define a function of the control channel burst protocol for controlling a MAC message to be transmitted over the common MAC channel in a stacked protocol structure.
Further, as illustrated in FIGS. 2 and 3, in an existing CDMA mobile communication system, since the above function is performed in their respective corresponding protocol entities, there are required three protocol entities. This means that one system has overlapped function blocks, causing an increase in system complexity and difficulty in realizing the system. That is, the protocol entities independently manage areas for storing the data related to the sequence number, thus causing a waste of storage.
In addition, with regard to the control message generated in Layer 3, since the address function block is located at an upper part of the MAC sublayer, an increased processor load may arise which processes every Layer 3 control message transmitted from the MAC sublayer to the common signaling channel and transfers it to the upper link access control sublayer.
It is, therefore, an object of the present invention to provide a method for transmitting a MAC message through a control channel burst protocol with increased reliability when transmitting the MAC message over a common MAC channel in a CDMA communication system.
It is another object of the present invention to provide a method for unifying, into one entity, common function blocks of separate protocol entities for processing a Layer 3 control message, user data and a MAC message, to be transmitted over a common channel, in a CDMA communication system.
It is a further object of the present invention to provide a method for reducing system complexity by unifying overlapped function blocks, thereby simplifying realization of the system and increasing system performance.
It is still another object of the present invention to provide a method for reducing a load on a MAC sublayer by placing an address function block in a MAC function block.
The present invention is a novel method for processing a common channel message comprising the steps of: mapping a signaling message generated in Layer 3, a medium access control (MAC) message generated in a MAC sublayer and user data, to be transmitted over common channels, to corresponding common logical channels; adding an identifier identifying each corresponding common logical channel to each message; processing the common logical channel identifier-added messages according to a common radio burst protocol using a single sequence number; and mapping the messages processed according to the common radio burst protocol to corresponding common channels.
To process the common logical channel identifier-added messages, the method further includes adding an automatic repeat request (ARQ) parameter including a message sequence number and an acknowledgement sequence number to the common logical channel identifier-added message; adding an address parameter including a control field for identifying a mobile station to the ARQ parameter-added message, to identify data transmitter or receiver; and adding a message length field and a cyclic redundancy check (CRC) field to the address parameter-added message, to frame the message.